The International Space Station is a permanently inhabited facility in low Earth orbit, jointly established to carry out space activities by the space agencies of Europe, the United States, Russia, Canada, and Japan. Roscosmos (The Russian Space Agency) and NASA (National Aeronautics and Space Administration) are in disagreement regarding an air leak that has occurred on the International Space Station (ISS). The existing leak is located in a section called PrK of the Zvezda service module, which is part of the Russian segment of the station, and both parties are aware of it since 2019. According to a report published by NASA’s Office of Inspector General (OIG) in September (hereinafter “NASA2030”), cracks and air leaks in the Service Module Transfer Tunnel have reached their highest levels, posing a significant safety risk. 

NASA and Roscosmos “don’t have a common understanding” of the likely root causes or the severity of the consequences of these leaks. NASA officials believe that the cracks in the PrK module are likely caused by multiple factors, including pressure and mechanical stress, residual stress, material properties, and environmental exposure. 

NASA often uses a 5×5 “risk matrix” to classify the likelihood and consequences of risks to spaceflight activities, and the Russian leaks are now rated as “5” for both high likelihood and high consequence, raising concerns that the issue could ultimately lead to a catastrophic failure. On the other hand, Roscosmos officials emphasize that the leak poses no threat to the crew’s safety. They suggest that the cracks are likely caused by high-cycle fatigue due to micro-vibrations and consider a catastrophic failure of the PrK module to be an unlikely scenario. Since the parties could not reach a common understanding and the investigations are still ongoing, they decided to keep the hatch(a sealed door  that allows astronauts to move between different modules of the space station while maintaining airtight integrity) between the Russian and U.S. segments closed as a temporary solution (As can be seen here, here, here, and here). 

In this blog post, I will examine the legal framework governing this ongoing air-leak dispute, outline the responsibilities and potential liabilities of the ISS partner states under the 1998 Intergovernmental Agreement, the Outer Space Treaty and the Liability Convention, and assess how international law responds to safety risks occurring aboard the International Space Station.

Applicable Law in the ISS Air Leak Crisis

There is a specific multilateral agreement addressing issues that may arise on the International Space Station, the 1998 Intergovernmental Agreement (hereinafter “IGA1998”) on the ISS. Additionally, the Outer Space Treaty (OST), the Liability Convention (hereinafter “LIAB”), the Rescue Agreement, and Registration Convention also apply in this context, as these agreements regulate matters concerning spacecraft and their components, as well as the rescue and return of astronauts, both in space and on Earth, including the ISS. The implementation, interpretation, and determination of state responsibility under an international treaty shall be carried out in accordance with the general provisions (see, Arts.31-32) of the Vienna Convention on the Law of Treaties. In this regard, OST, 1998 IGA and LIAB will be evaluated accordingly, and any deficiencies will be addressed in line with this approach. (See p.113)

The development, construction, and operation of the ISS must be seen and interpreted in the light of the aforementioned international treaties, and customary international law – Which are the governing rules for the Outer Space – and, in cases where the IGA on the ISS (1998) is insufficient, these other agreements provide supplementary application (see p. 1038), as stated in Article 2 of the 1998 Multilateral Agreement, which affirms that other agreements will apply to the ISS. 

• Partner states’ responsibilities in space station operations under the IGA

Article 1 of the IGA includes a provision that governs long-term international cooperation between states. This article specifically defines the civil ISS program and outlines the nature of the partnership, detailing the rights and obligations of each participating partner in the collaboration.

According to Article VII, paragraph 2, NASA is responsible for the overall program management and coordination, system engineering, safety requirements and plans, as well as the planning and coordination of the execution of the integrated operation of the ISS (IGA 1998). At the same time, Roscosmos holds a major responsibility in the operation of the ISS, contributing to the Russian Segment (the Zarya and Zvezda). These modules not only served as the initial living quarters and control center for the ISS but continue to play an essential role in the station’s ongoing operations, making Roscosmos a crucial partner in the functioning and success of the space station.

Additionally, Articles 7 and 9 of the Intergovernmental Agreement (IGA) outline the responsibilities of the partners regarding the management, operation, and utilization of the ISS. In this matter, Article 7 of the IGA governs the management of the ISS, placing a responsibility on partners and cooperating agencies to ensure and coordinate its safe, efficient, and effective operation. According to this article, States Parties are required to operate the station in a manner that safeguards the safety of both the station and the astronauts on board. In line with this obligation, Russia was expected to operate the module in a way that prevented any damage.

Article 9, paragraph 4 of the IGA regulates ‘utilization’ and states that “In its use of the Space Station, each Partner, through its Cooperating Agency, shall seek through the mechanisms established in the MOUs to avoid causing serious adverse effects on the use of the Space Station by the other Partners.”

According to this provision, partners are obligated to avoid causing any ‘serious adverse effects’ that could negatively impact the operations or usage of the Space Station by other partners.  As required by this obligation, Russia was expected to avoid any serious adverse effects and to take appropriate measures to that end.

• Partner states’ responsibilities in space station operations under the OST

As the 1998 IGA does not provide detailed rules concerning harmful contamination, the potential risks to astronauts, or liability, it is necessary, for the resolution of the present dispute, to invoke and apply the relevant provisions of OST.

Under Article IX of the OST, States Parties are obligated to implement “appropriate measures” to prevent harmful contamination and engage in cooperation to ensure the responsible use of outer space.

Article IX of the OST obliges States to take appropriate measures to prevent harmful contamination.  However, it is not specified what constitutes an appropriate measure. Therefore, what constitutes appropriate measures to prevent harmful contamination may be interpreted in terms of the principle of “due regard” (see p.290) for the interests of other States Parties. Consequently, the measure to be taken (see p.36) must be carried out with a certain standard of care, attention or observance and must be appropriate to reduce harmful contamination of outer space.

The air leak has been identified since 2019, and recent reports indicate a notable increase in its severity. While no harm has occurred so far, Roscosmos must take the appropriate measures in case the space station requires more fuel or if future damage occurs due to the leak. In order to prevent such outcomes, Roscosmos must take appropriate measures in line with the principle of “due regard” for the safety and operations of the space station.

Art. IX provides that States Parties shall act in accordance with the principle of co-operation and mutual assistance in the exploration and use of outer space. The principle of co-operation and mutual assistance imposes a limitation on the freedom of States to operate in outer space. Therefore, when states engage in any activity, especially one that may affect others, they should cooperate and consult in such cases.

Roscosmos has held discussions with NASA on multiple occasions regarding the air leak issue, in line with the principle of cooperation. Therefore, we can submit that Roscosmos has adhered to this principle.

• Partners’ Liability under IGA and the Liability Convention
  • Explanation of The Cross-waiver of Liability among IGA Partner States

Article 16/3-a of the IGA establishes a cross waiver of liability among Partners and related entities, encouraging participation in space exploration and the use of the Space Station. Cross-waiver of liability is agreed not to sue each other for damages arising from space-related activities. Each party assumes responsibility for its own risks and losses, even if another party’s actions contributed to them. Under Article 16, Partner States cannot assert liability claims against each other concerning Protected Space Operations (IGA 1998 Art.16/3-a). 

This waiver of liability also extends to the Liability Convention, meaning that Partner States cannot be held liable to one another under this framework (IGA 1998 Art.16/3-b). The definition and scope of Protected Space Operations are explicitly outlined in paragraph 2, subparagraph (f) of the same article, which states that this term encompasses all ISS activities.

In the case of the air leak incident, since the issue concerns a module that falls within the scope of the Space Station activities, which are classified as Protected Space Operations, any resulting damage would not create liability for one Partner State toward another under either the IGA or the Liability Convention. Therefore, no Partner of IGA, including NASA, can hold Roscosmos liable for a breach of obligations under international space law.

• • Liability for Third-Party Claims

The ISS is not exclusively used by the IGA Partner States. While the Partner States play a significant role in the ISS’s management, it is also accessible and used by non-Partner States. As outlined in Article 17, paragraph 2, if a third-party non-signatory State makes an accusation against a Partner State, the Partners must collectively defend and negotiate the matter. Based on this provision, a third-party State or entity may bring liability claims against the IGA Partner States, and the provisions of the Liability Convention may also apply in this context.

If a third party suffers damage due to an air leak, the cross-waiver of liability will no longer apply, and the Partner Roscosmos may be held liable under the Liability Convention. Nevertheless, for liability to be established under the Liability Convention, certain conditions must be satisfied: (1) the damage must be caused by a space object, (2) actual damage must occur, and (3) there must be a clear causal link between the damage and the space object.(LIAB Art.2 and 3) Additionally, if the liability falls under fault-based liability as outlined in Article III of the Liability Convention, it must also be established that the damage resulted from the fault of Roscosmos.

• • Circumstances Where Cross-waiver Does Not Apply

The IGA also outlines specific situations that are excluded from the scope of the cross-waiver of liability, meaning the cross-waiver does not apply in these cases. According to Article 16 paragraph 3(d), the liability applies to: (1) Claims between a Partner State and its related entities, or between its own related entities; (2) Claims made by a natural person, or their estate, survivors, or successors (unless the successor is a Partner State), for bodily injury, health impairment, or death; (3) Claims for damages resulting from willful misconduct; (4) Claims related to intellectual property rights. Accordingly, if the air leak causes harm to a natural person in the future or results in death, or if it is determined that ROSCOSMOS engaged in willful misconduct in causing the damage, the cross-waiver of liability will no longer be applicable.

• Ensuring Astronaut Safety: Obligations Under Article 5 of the Outer Space Treaty

Another important issue is the safety of the astronauts serving on the ISS. Article 5 of the OST considers astronauts to be envoys of mankind in outer space and regulates their safety. According to this Article, States Parties to the Treaty shall immediately inform the other States Parties to the Treaty or the Secretary-General of the UN of any phenomena they discover in outer space, including the Moon and other celestial bodies, which could constitute a danger to the life or health of astronauts. To ensure the astronauts’ safety, it is essential that not only the partners but all countries provide the necessary security for every space crew.

Conclusion

As a result, the ongoing air leak is significantly disrupting space activities. This not only affects the countries currently engaged in space operations but also undermines the right to conduct space activities, which is considered the common heritage of all mankind, including states that may engage in such activities in the future. So far, only the hatch has been sealed as a precaution. However, according to NASA, closing the service module hatch does not eliminate the danger. While permanent closure would allow the ISS to continue functioning, it could impact cargo deliveries by reducing the number of available delivery ports and would require additional propellant to maintain the Station’s altitude and attitude (see NASA 2030, p.11).

The lack of clear definitions in existing agreements regarding the allocation of future damages and responsibility is a major concern. If one of the partners fails to exercise due care in conducting its activities, or does not remediate the damage caused despite such failure, it pushes the limits of responsible space activity. Therefore, the air leak must be addressed immediately to prevent further issues and to ensure that space activities can continue safely.